Copied project3 to project4
Added startup code
Added function start and exit code (but not yet shift sp)
Added write_string, write_int stack io function
Added size, offset in struct decl, Added local variable offset, Added assign code
Added global variable offset, Added global variable data access"
Reducing binary -> unary, Removed decl -> type transition (decl propagation)
Added unary not, unary negate generation code
Added array access generation code, Fixed const_expr -> INTEGER_CONST in array definition
Fixed const_expr -> INTEGER_CONST in array definitions, Added struct access generation code
Added binary operation generation code
Added logical or, logical and code generation
Added if, else code generation. Fixed EQUOP code generation
Added function call generation code. Added while, for statement generation code